/*
 * jdsample.c
 *
 * Copyright (C) 1991-1994, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains upsampling routines.
 *
 * Upsampling input data is counted in "row groups".  A row group
 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
 * sample rows of each component.  Upsampling will normally produce
 * max_v_samp_factor pixel rows from each row group (but this could vary
 * if the upsampler is applying a scale factor of its own).
 *
 * An excellent reference for image resampling is
 *   Digital Image Warping, George Wolberg, 1990.
 *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/* Pointer to routine to upsample a single component */
typedef JMETHOD ( void, upsample1_ptr,
                 ( j_decompress_ptr cinfo, jpeg_component_info * compptr,
                   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) );

/* Private subobject */

typedef struct {
    struct jpeg_upsampler pub;  /* public fields */

    /* Color conversion buffer.  When using separate upsampling and color
     * conversion steps, this buffer holds one upsampled row group until it
     * has been color converted and output.
     * Note: we do not allocate any storage for component(s) which are full-size,
     * ie do not need rescaling.  The corresponding entry of color_buf[] is
     * simply set to point to the input data array, thereby avoiding copying.
     */
    JSAMPARRAY color_buf[MAX_COMPONENTS];

    /* Per-component upsampling method pointers */
    upsample1_ptr methods[MAX_COMPONENTS];

    int        next_row_out; /* counts rows emitted from color_buf */
    JDIMENSION rows_to_go;  /* counts rows remaining in image */

    /* Height of an input row group for each component. */
    int rowgroup_height[MAX_COMPONENTS];

    /* These arrays save pixel expansion factors so that int_expand need not
     * recompute them each time.  They are unused for other upsampling methods.
     */
    UINT8 h_expand[MAX_COMPONENTS];
    UINT8 v_expand[MAX_COMPONENTS];
} my_upsampler;

typedef my_upsampler * my_upsample_ptr;


/*
 * Initialize for an upsampling pass.
 */

METHODDEF void
start_pass_upsample( j_decompress_ptr cinfo ) {
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

    /* Mark the conversion buffer empty */
    upsample->next_row_out = cinfo->max_v_samp_factor;
    /* Initialize total-height counter for detecting bottom of image */
    upsample->rows_to_go = cinfo->output_height;
}


/*
 * Control routine to do upsampling (and color conversion).
 *
 * In this version we upsample each component independently.
 * We upsample one row group into the conversion buffer, then apply
 * color conversion a row at a time.
 */

METHODDEF void
sep_upsample( j_decompress_ptr cinfo,
              JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
              JDIMENSION in_row_groups_avail,
              JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
              JDIMENSION out_rows_avail ) {
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    int ci;
    jpeg_component_info * compptr;
    JDIMENSION num_rows;

    /* Fill the conversion buffer, if it's empty */
    if ( upsample->next_row_out >= cinfo->max_v_samp_factor ) {
        for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
              ci++, compptr++ ) {
            /* Invoke per-component upsample method.  Notice we pass a POINTER
             * to color_buf[ci], so that fullsize_upsample can change it.
             */
            ( *upsample->methods[ci] )( cinfo, compptr,
                                        input_buf[ci] + ( *in_row_group_ctr * upsample->rowgroup_height[ci] ),
                                        upsample->color_buf + ci );
        }
        upsample->next_row_out = 0;
    }

    /* Color-convert and emit rows */

    /* How many we have in the buffer: */
    num_rows = (JDIMENSION) ( cinfo->max_v_samp_factor - upsample->next_row_out );
    /* Not more than the distance to the end of the image.  Need this test
     * in case the image height is not a multiple of max_v_samp_factor:
     */
    if ( num_rows > upsample->rows_to_go ) {
        num_rows = upsample->rows_to_go;
    }
    /* And not more than what the client can accept: */
    out_rows_avail -= *out_row_ctr;
    if ( num_rows > out_rows_avail ) {
        num_rows = out_rows_avail;
    }

    ( *cinfo->cconvert->color_convert )( cinfo, upsample->color_buf,
                                         (JDIMENSION) upsample->next_row_out,
                                         output_buf + *out_row_ctr,
                                         (int) num_rows );

    /* Adjust counts */
    *out_row_ctr += num_rows;
    upsample->rows_to_go -= num_rows;
    upsample->next_row_out += num_rows;
    /* When the buffer is emptied, declare this input row group consumed */
    if ( upsample->next_row_out >= cinfo->max_v_samp_factor ) {
        ( *in_row_group_ctr )++;
    }
}


/*
 * These are the routines invoked by sep_upsample to upsample pixel values
 * of a single component.  One row group is processed per call.
 */


/*
 * For full-size components, we just make color_buf[ci] point at the
 * input buffer, and thus avoid copying any data.  Note that this is
 * safe only because sep_upsample doesn't declare the input row group
 * "consumed" until we are done color converting and emitting it.
 */

METHODDEF void
fullsize_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
                   JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
    *output_data_ptr = input_data;
}


/*
 * This is a no-op version used for "uninteresting" components.
 * These components will not be referenced by color conversion.
 */

METHODDEF void
noop_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
               JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
    *output_data_ptr = NULL;/* safety check */
}


/*
 * This version handles any integral sampling ratios.
 * This is not used for typical JPEG files, so it need not be fast.
 * Nor, for that matter, is it particularly accurate: the algorithm is
 * simple replication of the input pixel onto the corresponding output
 * pixels.  The hi-falutin sampling literature refers to this as a
 * "box filter".  A box filter tends to introduce visible artifacts,
 * so if you are actually going to use 3:1 or 4:1 sampling ratios
 * you would be well advised to improve this code.
 */

METHODDEF void
int_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
              JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    JSAMPARRAY output_data = *output_data_ptr;
    register JSAMPROW inptr, outptr;
    register JSAMPLE invalue;
    register int h;
    JSAMPROW outend;
    int h_expand, v_expand;
    int inrow, outrow;

    h_expand = upsample->h_expand[compptr->component_index];
    v_expand = upsample->v_expand[compptr->component_index];

    inrow = outrow = 0;
    while ( outrow < cinfo->max_v_samp_factor ) {
        /* Generate one output row with proper horizontal expansion */
        inptr = input_data[inrow];
        outptr = output_data[outrow];
        outend = outptr + cinfo->output_width;
        while ( outptr < outend ) {
            invalue = *inptr++;/* don't need GETJSAMPLE() here */
            for ( h = h_expand; h > 0; h-- ) {
                *outptr++ = invalue;
            }
        }
        /* Generate any additional output rows by duplicating the first one */
        if ( v_expand > 1 ) {
            jcopy_sample_rows( output_data, outrow, output_data, outrow + 1,
                               v_expand - 1, cinfo->output_width );
        }
        inrow++;
        outrow += v_expand;
    }
}


/*
 * Fast processing for the common case of 2:1 horizontal and 1:1 vertical.
 * It's still a box filter.
 */

METHODDEF void
h2v1_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
               JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
    JSAMPARRAY output_data = *output_data_ptr;
    register JSAMPROW inptr, outptr;
    register JSAMPLE invalue;
    JSAMPROW outend;
    int inrow;

    for ( inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++ ) {
        inptr = input_data[inrow];
        outptr = output_data[inrow];
        outend = outptr + cinfo->output_width;
        while ( outptr < outend ) {
            invalue = *inptr++;/* don't need GETJSAMPLE() here */
            *outptr++ = invalue;
            *outptr++ = invalue;
        }
    }
}


/*
 * Fast processing for the common case of 2:1 horizontal and 2:1 vertical.
 * It's still a box filter.
 */

METHODDEF void
h2v2_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
               JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
    JSAMPARRAY output_data = *output_data_ptr;
    register JSAMPROW inptr, outptr;
    register JSAMPLE invalue;
    JSAMPROW outend;
    int inrow, outrow;

    inrow = outrow = 0;
    while ( outrow < cinfo->max_v_samp_factor ) {
        inptr = input_data[inrow];
        outptr = output_data[outrow];
        outend = outptr + cinfo->output_width;
        while ( outptr < outend ) {
            invalue = *inptr++;/* don't need GETJSAMPLE() here */
            *outptr++ = invalue;
            *outptr++ = invalue;
        }
        jcopy_sample_rows( output_data, outrow, output_data, outrow + 1,
                           1, cinfo->output_width );
        inrow++;
        outrow += 2;
    }
}


/*
 * Fancy processing for the common case of 2:1 horizontal and 1:1 vertical.
 *
 * The upsampling algorithm is linear interpolation between pixel centers,
 * also known as a "triangle filter".  This is a good compromise between
 * speed and visual quality.  The centers of the output pixels are 1/4 and 3/4
 * of the way between input pixel centers.
 *
 * A note about the "bias" calculations: when rounding fractional values to
 * integer, we do not want to always round 0.5 up to the next integer.
 * If we did that, we'd introduce a noticeable bias towards larger values.
 * Instead, this code is arranged so that 0.5 will be rounded up or down at
 * alternate pixel locations (a simple ordered dither pattern).
 */

METHODDEF void
h2v1_fancy_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
                     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
    JSAMPARRAY output_data = *output_data_ptr;
    register JSAMPROW inptr, outptr;
    register int invalue;
    register JDIMENSION colctr;
    int inrow;

    for ( inrow = 0; inrow < cinfo->max_v_samp_factor; inrow++ ) {
        inptr = input_data[inrow];
        outptr = output_data[inrow];
        /* Special case for first column */
        invalue = GETJSAMPLE( *inptr++ );
        *outptr++ = (JSAMPLE) invalue;
        *outptr++ = (JSAMPLE) ( ( invalue * 3 + GETJSAMPLE( *inptr ) + 2 ) >> 2 );

        for ( colctr = compptr->downsampled_width - 2; colctr > 0; colctr-- ) {
            /* General case: 3/4 * nearer pixel + 1/4 * further pixel */
            invalue = GETJSAMPLE( *inptr++ ) * 3;
            *outptr++ = (JSAMPLE) ( ( invalue + GETJSAMPLE( inptr[-2] ) + 1 ) >> 2 );
            *outptr++ = (JSAMPLE) ( ( invalue + GETJSAMPLE( *inptr ) + 2 ) >> 2 );
        }

        /* Special case for last column */
        invalue = GETJSAMPLE( *inptr );
        *outptr++ = (JSAMPLE) ( ( invalue * 3 + GETJSAMPLE( inptr[-1] ) + 1 ) >> 2 );
        *outptr++ = (JSAMPLE) invalue;
    }
}


/*
 * Fancy processing for the common case of 2:1 horizontal and 2:1 vertical.
 * Again a triangle filter; see comments for h2v1 case, above.
 *
 * It is OK for us to reference the adjacent input rows because we demanded
 * context from the main buffer controller (see initialization code).
 */

METHODDEF void
h2v2_fancy_upsample( j_decompress_ptr cinfo, jpeg_component_info * compptr,
                     JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr ) {
    JSAMPARRAY output_data = *output_data_ptr;
    register JSAMPROW inptr0, inptr1, outptr;
#if BITS_IN_JSAMPLE == 8
    register int thiscolsum, lastcolsum, nextcolsum;
#else
    register INT32 thiscolsum, lastcolsum, nextcolsum;
#endif
    register JDIMENSION colctr;
    int inrow, outrow, v;

    inrow = outrow = 0;
    while ( outrow < cinfo->max_v_samp_factor ) {
        for ( v = 0; v < 2; v++ ) {
            /* inptr0 points to nearest input row, inptr1 points to next nearest */
            inptr0 = input_data[inrow];
            if ( v == 0 ) {/* next nearest is row above */
                inptr1 = input_data[inrow - 1];
            } else {/* next nearest is row below */
                inptr1 = input_data[inrow + 1];
            }
            outptr = output_data[outrow++];

            /* Special case for first column */
            thiscolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ );
            nextcolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ );
            *outptr++ = (JSAMPLE) ( ( thiscolsum * 4 + 8 ) >> 4 );
            *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + nextcolsum + 7 ) >> 4 );
            lastcolsum = thiscolsum;
            thiscolsum = nextcolsum;

            for ( colctr = compptr->downsampled_width - 2; colctr > 0; colctr-- ) {
                /* General case: 3/4 * nearer pixel + 1/4 * further pixel in each */
                /* dimension, thus 9/16, 3/16, 3/16, 1/16 overall */
                nextcolsum = GETJSAMPLE( *inptr0++ ) * 3 + GETJSAMPLE( *inptr1++ );
                *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + lastcolsum + 8 ) >> 4 );
                *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + nextcolsum + 7 ) >> 4 );
                lastcolsum = thiscolsum;
                thiscolsum = nextcolsum;
            }

            /* Special case for last column */
            *outptr++ = (JSAMPLE) ( ( thiscolsum * 3 + lastcolsum + 8 ) >> 4 );
            *outptr++ = (JSAMPLE) ( ( thiscolsum * 4 + 7 ) >> 4 );
        }
        inrow++;
    }
}


/*
 * Module initialization routine for upsampling.
 */

GLOBAL void
jinit_upsampler( j_decompress_ptr cinfo ) {
    my_upsample_ptr upsample;
    int ci;
    jpeg_component_info * compptr;
    boolean need_buffer, do_fancy;
    int h_in_group, v_in_group, h_out_group, v_out_group;

    upsample = (my_upsample_ptr)
               ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                            SIZEOF( my_upsampler ) );
    cinfo->upsample = (struct jpeg_upsampler *) upsample;
    upsample->pub.start_pass = start_pass_upsample;
    upsample->pub.upsample = sep_upsample;
    upsample->pub.need_context_rows = FALSE;/* until we find out differently */

    if ( cinfo->CCIR601_sampling ) {/* this isn't supported */
        ERREXIT( cinfo, JERR_CCIR601_NOTIMPL );
    }

    /* jdmainct.c doesn't support context rows when min_DCT_scaled_size = 1,
     * so don't ask for it.
     */
    do_fancy = cinfo->do_fancy_upsampling && cinfo->min_DCT_scaled_size > 1;

    /* Verify we can handle the sampling factors, select per-component methods,
     * and create storage as needed.
     */
    for ( ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
          ci++, compptr++ ) {
        /* Compute size of an "input group" after IDCT scaling.  This many samples
         * are to be converted to max_h_samp_factor * max_v_samp_factor pixels.
         */
        h_in_group = ( compptr->h_samp_factor * compptr->DCT_scaled_size ) /
                     cinfo->min_DCT_scaled_size;
        v_in_group = ( compptr->v_samp_factor * compptr->DCT_scaled_size ) /
                     cinfo->min_DCT_scaled_size;
        h_out_group = cinfo->max_h_samp_factor;
        v_out_group = cinfo->max_v_samp_factor;
        upsample->rowgroup_height[ci] = v_in_group;/* save for use later */
        need_buffer = TRUE;
        if ( !compptr->component_needed ) {
            /* Don't bother to upsample an uninteresting component. */
            upsample->methods[ci] = noop_upsample;
            need_buffer = FALSE;
        } else if ( h_in_group == h_out_group && v_in_group == v_out_group ) {
            /* Fullsize components can be processed without any work. */
            upsample->methods[ci] = fullsize_upsample;
            need_buffer = FALSE;
        } else if ( h_in_group * 2 == h_out_group &&
                    v_in_group == v_out_group ) {
            /* Special cases for 2h1v upsampling */
            if ( ( do_fancy ) && ( compptr->downsampled_width > 2 ) ) {
                upsample->methods[ci] = h2v1_fancy_upsample;
            } else {
                upsample->methods[ci] = h2v1_upsample;
            }
        } else if ( h_in_group * 2 == h_out_group &&
                    v_in_group * 2 == v_out_group ) {
            /* Special cases for 2h2v upsampling */
            if ( ( do_fancy ) && ( compptr->downsampled_width > 2 ) ) {
                upsample->methods[ci] = h2v2_fancy_upsample;
                upsample->pub.need_context_rows = TRUE;
            } else {
                upsample->methods[ci] = h2v2_upsample;
            }
        } else if ( ( h_out_group % h_in_group ) == 0 &&
                   ( v_out_group % v_in_group ) == 0 ) {
            /* Generic integral-factors upsampling method */
            upsample->methods[ci] = int_upsample;
            upsample->h_expand[ci] = (UINT8) ( h_out_group / h_in_group );
            upsample->v_expand[ci] = (UINT8) ( v_out_group / v_in_group );
        } else {
            ERREXIT( cinfo, JERR_FRACT_SAMPLE_NOTIMPL );
        }
        if ( need_buffer ) {
            upsample->color_buf[ci] = ( *cinfo->mem->alloc_sarray )
                                      ( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                       (JDIMENSION) jround_up( (long) cinfo->output_width,
                                                              (long) cinfo->max_h_samp_factor ),
                                       (JDIMENSION) cinfo->max_v_samp_factor );
        }
    }
}
